SVT vs. Fast Flutter

[SuckySurgeon7]

Hey all,

I'm a medical student trying to figure out how to differentiate a 2:1 flutter from SVT when looking at a 12 lead? An earlier thread (several years ago) mentioned giving adenosine and then watching for the P wave or sawtooth waves. Just wondering if I'm missing something on the twelve lead.

Thanks!

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[Rendar5]

Hey all,

I'm a medical student trying to figure out how to differentiate a 2:1 flutter from SVT when looking at a 12 lead? An earlier thread (several years ago) mentioned giving adenosine and then watching for the P wave or sawtooth waves. Just wondering if I'm missing something on the twelve lead.


Thanks!

In general a 2 to 1 flutter will not go as fast as an SVT. Maxing out at 160 I'm guessing

 

[gman33]

I had a case just like this yesterday.
Rate was pretty steady around 150.
Old guy with no similar hx.
Also had another acute medical issue which had me worried about slowing him down.

I gave him a low dose of cardizem.
Slowed down and then went into nsr.

Still don't know what rhythm he was really in, and it probably didn't matter in that case.

I've used calcium channel blockers in Svt.
Limited numbers but good success.
Patients like it a lot more than adenosine.
Verapamil is probably better than cardizem, but we don't have that in my Ed.

 

[shoal]

svt will be incrediblely regular almost no beat to best variability. march out the best to beat or fold the ekg over. any variation likely flutter or fib

Sent from my VS986 using Tapatalk

 

[canigetawhatwhat]

svt will be incrediblely regular almost no beat to best variability. march out the best to beat or fold the ekg over. any variation likely flutter or fib

Sent from my VS986 using Tapatalk

Not true.

Svt vs flutter is usually pretty easy. Slow it down and look for p waves. Flutter can very often not fluctuate.

Flutter vs sinus tach can be a lil hard. Usually jf its going rock solid at 150 without variability, its flutter.

Diagnostic adenosine for the win.

 

[gro2001]

First of all, try to get in the habit of using the right terms. Technically, all tachycardias apart from VT and V-fib (including sinus tachycardia) are SVT since they originate above the ventricles. Most people when they say SVT mean AVNRT, but some also mean AVRT while others are talking about AVNRT exclusively.

In terms of differentiating AVNRT from A-flutter pre-adenosine, as above posters have mentioned, other than history (if they had one of those before, it's probably that one) the two biggest clues are going to be:

1) Variability. While both atrial flutter and AVNRT are classified as 'regular' rhythms, atrial flutter can and often does have a variable block. Meaning the atrial rate is going as high as it possibly can, around 300, and the ventricles go at some fraction of that, 150 in 2:1 block, 100 in 3:1, etc. If you see the rate jump but clearly stay in that arrhythmia, it's not AVNRT which HAS to be extremely regular. This is because the ventricular beats are being fired off from a reentry current within the AV node itself, and since the speed of depolarization and size of the AV node are constant, it has almost no variability (<10% beat-to-beat variability). AVNRT can't slow down. It's either on or off.

2) Ventricular rate. Atrial flutter will typically be in the fractions of 300 I described (+/- 10 beats or so, typically) and rarely go above 150 (+/- 10). AVNRT on the other hand can't really go below 180 or so (since as I mentioned above, the speed of depolarization and the size of the AV node are fixed) and is typically in the 180-250 range.

Now, differentiating AVRT can be a little trickier since the possible heart rate of AVRT is more variable. This is because the reentry circuit uses an accessory pathway away from the AV node, and this can be at a variable distance meaning that the length of the circuit is different from individual to individual, and the heart rate can therefore be anywhere between 150 to 250 or so. Differentiating AVRT from A-flutter will need two points:

1) Variability. Even though AVRT has a wider range of possible heart rates among different individuals with AVRT, in each particular individual it will almost always be fixed at one particular heart rate with little variability.

2) Orthodromic vs antidromic. It can go in either direction around the circle and some of the time it will be antidromic, causing a wide complex tachycardia, which will make it easy to distinguish from A-flutter but maybe not so easy from VT

 

[WilcoWorld]

This really confused me as a resident until I realized two things:
a) By assuming the worst, you'll pick a safe option.
b) Antidromic AVNRT is an UGLY ECG. In the words of an old attending of mine, "don't worry, you're not going to look at that ECG and wonder if you should give diltiazem."

Don't worry too much about differentiating "SVT" (really, AVRT, as mentioned above) from a flutter with 2:1 block. You can treat them largely the same, as long as you default to assuming the worst when things are uncertain. Worry about differentiating sinus tach from tachyarrhythmias, as those should be treated quite differently.

I think about it like this:
1 - Stable or unstable? If unstable-->cardiovert. It doesn't really matter if you have unstable a fib, unstable v tach, unstable orthodromic AVRT, etc...the answer is cardioversion (unless it's v fib, but hopefully that's obvious). If stable-->proceed to #2.
2 - Narrow or wide? If wide--> compare to old ECG to see if there's a preexisting wide QRS. If the wide QRS is the same morphology, then you're dealing with an SVT--->proceed to #4. If the morphology is different, or if you can't get an old ECG-->assume wide complex tachycardia and proceed to #3.
3 - Wide complex tachycardia without aberrancy- you're either dealing with V tach or antidromic AVNRT. In either case, if it's stable you can give procainamide. If it's unstable, shock.
4 - Narrow complex tachyarrhythmia, or tachyarrhythmia with preexisting bundle branch block. This can be a fib, a flutter, or orthodromic AVRT. Is it regular or irregular? If regular--> it's AVRT or a flutter, proceed to #5. If irregular--> a fib, proceed to #6.
5 - Give adenosine and run a rhythm strip. If it's simple AVRT you'll likely fix them. If it was actually a flutter, you'll see the flutter waves, and you can move to #6.
6 - You've got a fib or a flutter. In a thread with 46 posts (as of now) we had about 30 different management plans described. Pick your poison.

 

[Zebra Hunter]

This really confused me as a resident until I realized two things:
a) By assuming the worst, you'll pick a safe option.
b) Antidromic AVNRT is an UGLY ECG. In the words of an old attending of mine, "don't worry, you're not going to look at that ECG and wonder if you should give diltiazem."

Don't worry too much about differentiating "SVT" (really, AVRT, as mentioned above) from a flutter with 2:1 block. You can treat them largely the same, as long as you default to assuming the worst when things are uncertain. Worry about differentiating sinus tach from tachyarrhythmias, as those should be treated quite differently.

I think about it like this:
1 - Stable or unstable? If unstable-->cardiovert. It doesn't really matter if you have unstable a fib, unstable v tach, unstable orthodromic AVRT, etc...the answer is cardioversion (unless it's v fib, but hopefully that's obvious). If stable-->proceed to #2.
2 - Narrow or wide? If wide--> compare to old ECG to see if there's a preexisting wide QRS. If the wide QRS is the same morphology, then you're dealing with an SVT--->proceed to #4. If the morphology is different, or if you can't get an old ECG-->assume wide complex tachycardia and proceed to #3.
3 - Wide complex tachycardia without aberrancy- you're either dealing with V tach or antidromic AVNRT. In either case, if it's stable you can give procainamide. If it's unstable, shock.
4 - Narrow complex tachyarrhythmia, or tachyarrhythmia with preexisting bundle branch block. This can be a fib, a flutter, or orthodromic AVRT. Is it regular or irregular? If regular--> it's AVRT or a flutter, proceed to #5. If irregular--> a fib, proceed to #6.
5 - Give adenosine and run a rhythm strip. If it's simple AVRT you'll likely fix them. If it was actually a flutter, you'll see the flutter waves, and you can move to #6.
6 - You've got a fib or a flutter. In a thread with 46 posts (as of now) we had about 30 different management plans described. Pick your poison.

I think one caveat to all this (which I know the person I'm responding to is aware of) is that often times these "a-fib w/ rvr" and "SVT" are not the primary diagnosis. I'd say a sizable percentage of these patients that present with HR's >140 happen to have alternative diagnoses that are causing the tachycardia. I've lost count of the number of times I, one of my fellow residents, or one of my attendings was pushing dilt on a CHF exacerbation or septic patient (or recently a large pericardial effusion) The issue is that it's difficult to differentiate on initial presentation. Despite the 220-age that many learn in medical school, there is a large percentage of the elderly that will still be able to get up to the 160's. Unless the pt has a great story for acute onset of palpitations or a hx of SVT or A-fib w/ RVR telling you this feels exactly like the previous times, if the patient is stable I'm waiting until I at least get some lab work and a CXR before deciding to push meds.

 

[Angry Birds]

I find the EKG computer reading will often let me know that it is flutter, and then I'm like, "Oh yeah, it is!"

 

[SuckySurgeon7]

First of all, try to get in the habit of using the right terms. Technically, all tachycardias apart from VT and V-fib (including sinus tachycardia) are SVT since they originate above the ventricles. Most people when they say SVT mean AVNRT, but some also mean AVRT while others are talking about AVNRT exclusively.

In terms of differentiating AVNRT from A-flutter pre-adenosine, as above posters have mentioned, other than history (if they had one of those before, it's probably that one) the two biggest clues are going to be:

1) Variability. While both atrial flutter and AVNRT are classified as 'regular' rhythms, atrial flutter can and often does have a variable block. Meaning the atrial rate is going as high as it possibly can, around 300, and the ventricles go at some fraction of that, 150 in 2:1 block, 100 in 3:1, etc. If you see the rate jump but clearly stay in that arrhythmia, it's not AVNRT which HAS to be extremely regular. This is because the ventricular beats are being fired off from a reentry current within the AV node itself, and since the speed of depolarization and size of the AV node are constant, it has almost no variability (<10% beat-to-beat variability). AVNRT can't slow down. It's either on or off.

2) Ventricular rate. Atrial flutter will typically be in the fractions of 300 I described (+/- 10 beats or so, typically) and rarely go above 150 (+/- 10). AVNRT on the other hand can't really go below 180 or so (since as I mentioned above, the speed of depolarization and the size of the AV node are fixed) and is typically in the 180-250 range.

Now, differentiating AVRT can be a little trickier since the possible heart rate of AVRT is more variable. This is because the reentry circuit uses an accessory pathway away from the AV node, and this can be at a variable distance meaning that the length of the circuit is different from individual to individual, and the heart rate can therefore be anywhere between 150 to 250 or so. Differentiating AVRT from A-flutter will need two points:

1) Variability. Even though AVRT has a wider range of possible heart rates among different individuals with AVRT, in each particular individual it will almost always be fixed at one particular heart rate with little variability.

2) Orthodromic vs antidromic. It can go in either direction around the circle and some of the time it will be antidromic, causing a wide complex tachycardia, which will make it easy to distinguish from A-flutter but maybe not so easy from VT

This really confused me as a resident until I realized two things:
a) By assuming the worst, you'll pick a safe option.
b) Antidromic AVNRT is an UGLY ECG. In the words of an old attending of mine, "don't worry, you're not going to look at that ECG and wonder if you should give diltiazem."

Don't worry too much about differentiating "SVT" (really, AVRT, as mentioned above) from a flutter with 2:1 block. You can treat them largely the same, as long as you default to assuming the worst when things are uncertain. Worry about differentiating sinus tach from tachyarrhythmias, as those should be treated quite differently.

I think about it like this:
1 - Stable or unstable? If unstable-->cardiovert. It doesn't really matter if you have unstable a fib, unstable v tach, unstable orthodromic AVRT, etc...the answer is cardioversion (unless it's v fib, but hopefully that's obvious). If stable-->proceed to #2.
2 - Narrow or wide? If wide--> compare to old ECG to see if there's a preexisting wide QRS. If the wide QRS is the same morphology, then you're dealing with an SVT--->proceed to #4. If the morphology is different, or if you can't get an old ECG-->assume wide complex tachycardia and proceed to #3.
3 - Wide complex tachycardia without aberrancy- you're either dealing with V tach or antidromic AVNRT. In either case, if it's stable you can give procainamide. If it's unstable, shock.
4 - Narrow complex tachyarrhythmia, or tachyarrhythmia with preexisting bundle branch block. This can be a fib, a flutter, or orthodromic AVRT. Is it regular or irregular? If regular--> it's AVRT or a flutter, proceed to #5. If irregular--> a fib, proceed to #6.
5 - Give adenosine and run a rhythm strip. If it's simple AVRT you'll likely fix them. If it was actually a flutter, you'll see the flutter waves, and you can move to #6.
6 - You've got a fib or a flutter. In a thread with 46 posts (as of now) we had about 30 different management plans described. Pick your poison.

I learned. Much appreciated.

I find the EKG computer reading will often let me know that it is flutter, and then I'm like, "Oh yeah, it is!"

This made me chuckle. +1

 

[pianoman511]

Also, if its tough to tell then you can just obtain a double speed EKG (50 mm/sec instead of 25 mm/sec) so you can see if there are p-waves. No uncomfortable adenosine required. And never underestimate the utility of a good valsalva.

 

[goodoldalky]

Also, if its tough to tell then you can just obtain a double speed EKG (50 mm/sec instead of 25 mm/sec) so you can see if there are p-waves. No uncomfortable adenosine required. And never underestimate the utility of a good valsalva.

By good valsalva, this: http://rebelem.com/the-revert-trial-a-modified-valsalva-maneuver-to-convert-svt/

A couple of my partners and I have started doing it strictly this way this year and to be honest a normal valsalva is worthless and this one works.

 

[Psai]

By good valsalva, this: http://rebelem.com/the-revert-trial-a-modified-valsalva-maneuver-to-convert-svt/

A couple of my partners and I have started doing it strictly this way this year and to be honest a normal valsalva is worthless and this one works.

Makes me wonder how they figured it out. Were they just trying a valsalva and someone fell backwards?

 

[Angry Birds]

By good valsalva, this: http://rebelem.com/the-revert-trial-a-modified-valsalva-maneuver-to-convert-svt/

A couple of my partners and I have started doing it strictly this way this year and to be honest a normal valsalva is worthless and this one works.

I thought "valsalva" just meant "get the adenosine."

I heard about this modified valsalva on a podcast, but the video really helps visualize it. Seems pretty reasonable to try.

Other comments on the video: Man, I wish I had a British accent.

 

[TheDudeMD]

I think one caveat to all this (which I know the person I'm responding to is aware of) is that often times these "a-fib w/ rvr" and "SVT" are not the primary diagnosis. I'd say a sizable percentage of these patients that present with HR's >140 happen to have alternative diagnoses that are causing the tachycardia. I've lost count of the number of times I, one of my fellow residents, or one of my attendings was pushing dilt on a CHF exacerbation or septic patient (or recently a large pericardial effusion) The issue is that it's difficult to differentiate on initial presentation. Despite the 220-age that many learn in medical school, there is a large percentage of the elderly that will still be able to get up to the 160's. Unless the pt has a great story for acute onset of palpitations or a hx of SVT or A-fib w/ RVR telling you this feels exactly like the previous times, if the patient is stable I'm waiting until I at least get some lab work and a CXR before deciding to push meds.

This is so true. I wish we had a fancy shorter name for "patient with baseline afib now tachycardic due to hemodynamic compensatory reasons and not because of intrinsic electrical physiology reasons" to differentiate it from afib with RVR. Sometimes that old lady with afib with HR 130 doesn't need to have dilt pushed, she needs to have her sepsis treated.

 

[future_dr_house]

Error

 

[dchristismi]

I will admit that I pushed adenosine on a PE once. Yeah, it was just sinus tach. But I was sure of it by the time we finished the adenosine challenge.

I am also going to totally try the modified valsalva next SVT I get.

 

[TheBlueBlazer]

I think one caveat to all this (which I know the person I'm responding to is aware of) is that often times these "a-fib w/ rvr" and "SVT" are not the primary diagnosis. I'd say a sizable percentage of these patients that present with HR's >140 happen to have alternative diagnoses that are causing the tachycardia. I've lost count of the number of times I, one of my fellow residents, or one of my attendings was pushing dilt on a CHF exacerbation or septic patient (or recently a large pericardial effusion) The issue is that it's difficult to differentiate on initial presentation. Despite the 220-age that many learn in medical school, there is a large percentage of the elderly that will still be able to get up to the 160's. Unless the pt has a great story for acute onset of palpitations or a hx of SVT or A-fib w/ RVR telling you this feels exactly like the previous times, if the patient is stable I'm waiting until I at least get some lab work and a CXR before deciding to push meds.

This was a regular topic at our residency M&M. Never want to see the Face of Death like I did after the ICU attending pushed dilt for the tachycardia we later learned was because of her big PE. That was not a fun code.